I. Field of the Invention
Embodiments of the invention relate generally to digital linear amplification with nonlinear components (LINC) transmitters, and more particularly, to digital LINC transmitters that compensate for phase and amplitude mismatches between two signal paths.
II. Related Art
In recent communication systems, the necessity for efficient frequency spectrum usage leads to the use of modulation methods such as quadrature amplitude modulation (QAM), which modulates data not only on the phase but also on the amplitude of the carrier signal, and consequently generates a signal having non-constant envelope. To transmit a signal with a non-constant envelope, the systems typically use linear power amplifiers. However, linear power amplifiers are inefficient in power consumption. Alternatives to linear power amplifiers include non-linear power amplifiers, which are more efficient in terms of power usage. However, the use of non-linear power amplifiers for non-constant envelope signals generally requires linearization techniques such as back-off, predistortion, feedforward, feedback, envelope elimination and restoration (EER), linear amplification with nonlinear components (LINC) and so on. As for LINC, prior LINC systems have had much difficulty in handling amplitude and/or phase compensation due to the tight matching requirement between two signal pats for all the available channels, and accordingly have avoided the use of LINC transmitters.